CN114235797A - Method for rapidly and accurately measuring sulfate content in wet flue gas desulfurization gypsum - Google Patents
Method for rapidly and accurately measuring sulfate content in wet flue gas desulfurization gypsum Download PDFInfo
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- CN114235797A CN114235797A CN202111301955.7A CN202111301955A CN114235797A CN 114235797 A CN114235797 A CN 114235797A CN 202111301955 A CN202111301955 A CN 202111301955A CN 114235797 A CN114235797 A CN 114235797A
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Abstract
The invention provides a method for rapidly and accurately measuring the content of sulfate in wet flue gas desulfurization gypsum, which adopts a method of a potentiometric titrator and a photometric electrode to measure the content of sulfate in wet flue gas desulfurization gypsum. The results show that: the method has the advantages of high accuracy, simple operation, less interference and good reproducibility. The method is used for measuring the values of national first-grade standard substances, namely standard gypsum samples, the gypsum and the slurry of the desulfurization system, and a satisfactory analysis result is obtained. Through mathematical statistical analysis of the test results of the sulfate content in national standard substances and actual samples, the test result of the method is accurate and reliable, and the method has high accuracy, precision and standard recovery rate. In a power plant, the strong acid type cation exchange resin is a material commonly used in production, and does not need to be ordered additionally, and the method can obtain a test result only by directly titrating a sample by a potentiometric titrator after the sample is treated by the resin, and the potentiometric titrator is simple and convenient and rapid to operate and convenient to master by an analyst.
Description
Technical Field
The invention relates to the technical field of sulfate detection, in particular to a method for quickly and accurately determining the sulfate content in wet flue gas desulfurization gypsum.
Background
At present, limestone-gypsum wet desulphurization is the main flue gas desulphurization technology of coal-fired boilers which has been internationally realized for industrial application at present. Most of domestic manufacturers use the method to carry out desulfurization. The desulfurization mechanism is that the flue gas is introduced into an absorption tower, sulfur dioxide in the flue gas reacts with limestone (the main component is calcium carbonate) in spray slurry (the spray liquid is prepared by adding water into the limestone), and then the limestone is oxidized by oxidizing air from bottom to top to generate calcium sulfate, and the calcium sulfate is crystallized to form gypsum (calcium sulfate dihydrate) after reaching a certain saturation degree. The gypsum slurry is dewatered by hydraulic cyclone and vacuum to obtain usable by-product gypsum.
The main reactions in the desulfurization process are as follows:
1、SO2+H2O→H2SO3absorption reaction
2、CaCO3+H2SO3→CaSO3+CO2+H2O neutralization reaction
3、
Oxidation reaction
4、
Crystallization of
5、CaSO4+2H2O→CaSO4·2H2O crystal
From the above principle, it can be seen that in a wet flue gas desulfurization system, sulfate content in slurry and gypsum of an absorption tower needs to be accurately grasped in time, most units adopt a sulfate gravimetric method proposed in GB/T5484-2000 "gypsum chemical analysis method" to directly measure the sulfate content, but the sulfate gravimetric method has the problems that the measuring procedure is complicated, the measuring can be completed within two days, and when the system is abnormally operated or the operation condition changes and the sulfate content needs to be grasped in time, the sulfate gravimetric method has a certain hysteresis effect, so it is very important to explore a method for rapidly measuring the sulfate content in the wet flue gas desulfurization system.
Other methods for measuring the sulfate content in the environmental sample comprise ion chromatography, barium chromate photometry and barium chromate indirect atomic absorption, and the methods are mainly suitable for batch test of samples with low sulfate content and are not practical for test of desulfurization system samples with high sulfate content. In DL/T502.12-2006 thermal power plant water vapor analysis method-twelfth part: in the determination of sulfate (volumetric method), a barium chloride titration method is proposed, azoarsine III is used as an indicator, but when the method is actually applied to a desulfurization system, the color change of a titration end point is very unobvious, and a large determination error is easily generated.
Based on the above, the content of calcium sulfate dihydrate is back-deduced in many places from the determination of the water of crystallization of gypsum by means of a halogen moisture meter at 200 ℃. However, the accuracy of the method is reduced as the sulfate content in the desulfurized gypsum is reduced due to the influence of the sulfite content and the like in the desulfurized gypsum. By experimental control analysis, when the mass percentage concentration of the sulfate is lower than 90%, serious deviation occurs, and the indirect analysis method is not suitable for the determination of the gypsum sulfate.
The West-Ann thermal institute recommends a new method for determining the sulfate content of a flue gas desulfurization system in 2019, wherein hydrogen peroxide is added into a sample to be measured, sulfite in the sample is oxidized into sulfate, and then hydrogen type strong acid cation exchange resin is added to convert all cations in the sample into hydrogen ions. Titrating the exchanged effluent liquid by using a barium perchlorate standard solution, calculating the total amount of sulfate and sulfite in the sample according to the volume consumed by the barium perchlorate standard solution, and deducting the content of the sulfite to obtain the content of the sulfate in the sample.
However, in practical application, the number of samples required to be analyzed by actual operation conditions is large, and when the determination method is adopted, the barium perchlorate standard solution needs to be slowly dripped in the final process of precipitation titration, so that the labor intensity of analysts is high, the time consumption of the analysis process is long, the titration end point needs to be judged by the analysts subjectively, the accuracy is low, and the rapid and accurate determination of the samples is not facilitated.
Disclosure of Invention
The invention aims to provide a method for rapidly and accurately measuring the sulfate content in wet flue gas desulfurization gypsum.
The technical scheme for realizing the purpose is as follows:
a method for rapidly and accurately measuring the sulfate content in wet flue gas desulfurization gypsum comprises the following steps:
s1, weighing 0.25g of desulfurized gypsum sample, adding 10mL of H2O2Mixing with 10mL of demineralized water, and stirring;
s2, adding cation exchange resin, stirring and filtering;
s3, placing the filtrate in a 250mL volumetric flask, repeatedly filtering and washing until the liquid level of the solution is close to the bottleneck of the 250mL volumetric flask, and fixing the volume to 250mL by using desalted water;
s4, taking 10mL of constant volume solution, adding 10mL of acetone and 3 drops of sulfonic acid-III indicator, mixing, and adding desalted water until the color of the solution is just purple;
s5, titrating the solution titrated in the step S4 on a potentiometric titrator by using 0.005mol/L barium perchlorate until the color of the solution becomes light blue, and recording the volume V of the barium perchlorate consumed by titration.
Further, in the step S1, the mixture is stirred for 10min by using a magnetic stirrer.
Further, said H2O2The mass fraction is 30%.
Further, the cation exchange resin adopts strong acid type cation exchange resin.
Still further, the cation exchange resin was washed with demineralized water until the effluent pH was 7 prior to use.
Further, the mass fraction of the sulfonic acid-III is 0.1 percent; acetone was analytically pure.
Further, the potentiometric titrator employs a photometric electrode.
Further, the potentiometric titrator wavelength was set to 555 nm.
Still further, the method for calculating the sulfate content comprises the following steps:
in the formula:
m is the mass of the sample, g;
0.4003 is the conversion coefficient of barium perchlorate solution to sulfur trioxide of 0.0005 mol/L;
1.2498 is the conversion coefficient of sulfur dioxide to sulfur trioxide;
The invention has the beneficial effects that:
the invention provides a method for rapidly and accurately measuring the content of sulfate in wet flue gas desulfurization gypsum, which adopts a method of a potentiometric titrator and a photometric electrode to measure the content of sulfate in wet flue gas desulfurization gypsum. The results show that: the method has the advantages of high accuracy, simple operation, less interference and good reproducibility. The method is used for measuring the values of national first-grade standard substances, namely standard gypsum samples, the gypsum and the slurry of the desulfurization system, and a satisfactory analysis result is obtained. Through mathematical statistical analysis of the test results of the sulfate content in national standard substances and actual samples, the test result of the method is accurate and reliable, and the method has high accuracy, precision and standard recovery rate. In a power plant, the strong acid type cation exchange resin is a material commonly used in production, and does not need to be ordered additionally, and the method can obtain a test result only by directly titrating a sample by a potentiometric titrator after the sample is treated by the resin, and the potentiometric titrator is simple and convenient and rapid to operate and convenient to master by an analyst.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below. It should be apparent that the drawings in the following description are merely exemplary, and that other embodiments can be derived from the drawings provided by those of ordinary skill in the art without inventive effort.
FIG. 1 is a graph of the titration curve of example 1 of the present invention.
Detailed Description
To make the objects, technical solutions and advantages of the embodiments of the present invention clearer and more complete, the technical solutions in the embodiments of the present invention will be described below, obviously, the described embodiments are only a part of the embodiments of the present application, but not all embodiments, and the description is only for further explaining the features and advantages of the present invention, and not for limiting the claims of the present invention; all other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
The following detailed description of embodiments of the present invention is provided in connection with the accompanying drawings and examples. The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.
Example 1 Gypsum Standard analysis
0.2500g of sample was weighed into a beaker and 10mL of H was added2O2And 10mL of demineralized water, cover the petri dish, and stir with a magnetic stirrer for 10min. Then three spoons of cation exchange resin were added and stirred for 10min the sample was filtered with filter paper into a 250mL volumetric flask, the beaker was carefully rinsed with demineralized water, filtered until the solution level was close to the neck of the 250mL volumetric flask and the volume was brought to 250mL with demineralized water. Pipette 10mL into a beaker, add 10mL of acetone and 3 drops of sulfonic acid-III indicator, mix, and slowly add demineralized water until the solution color just turns purple. In potentiometric titratorsTitration was carried out with 0.005mol/L barium perchlorate until the solution became pale blue in color. The consumption volume V is recorded.
On the basis of the above examples, H2O2The mass fraction is 30 percent; the mass fraction of sulfonic acid-III is 0.1 percent; acetone was analytically pure.
Other test reagents: a0.005 mol/L standard sulfuric acid solution was used for calibration of barium perchlorate.
In addition to the above examples, cation exchange resins in strong acid form were used. The cation exchange resin was washed to neutrality before use.
In addition to the above examples, the potentiometric titrator was a Mettler DL58 potentiometric titrator, employing a photometric electrode, the wavelength was set at 555 nm.
The titration curve is shown in FIG. 1, and it can be seen from the titration curve that the end point of the reaction is determined when a breakthrough occurs at a certain ml of the titration volume.
Still further, the method for calculating the sulfate content comprises the following steps:
in the formula:
m is the mass of the sample, g;
0.4003 is the conversion coefficient of barium perchlorate solution to sulfur trioxide of 0.0005 mol/L;
1.2498 is the conversion coefficient of sulfur dioxide to sulfur trioxide;
The GSB 08-1352-:
TABLE 1 Experimental results for standard gypsum samples (in terms of SO in gypsum)3% represents
Example 2 desulfurization gypsum spiking analysis
Weighing 0.2500g of sample, placing the sample into a beaker, adding a certain amount of high-grade pure anhydrous sodium sulfate, and adding 10mL of H2O2And 10mL of demineralized water, cover the petri dish, and stir with a magnetic stirrer for 10min. Then three spoons of cation exchange resin were added and stirred for 10min the sample was filtered with filter paper into a 250mL volumetric flask, the beaker was carefully rinsed with demineralized water, filtered until the solution level was close to the neck of the 250mL volumetric flask and the volume was brought to 250mL with demineralized water. Pipette 10mL into a beaker, add 10mL of acetone and 3 drops of sulfonic acid-III indicator, mix, and slowly add demineralized water until the solution color just turns purple. Titration was carried out in a potentiometric titrator with 0.005mol/L barium perchlorate until the solution became pale blue in color. The consumption volume V is recorded.
Other test reagents: the high-grade pure anhydrous sodium sulfate is used for a standard addition experiment; 0.005mol/L standard sulfuric acid solution for calibrating barium perchlorate.
In addition to the above examples, cation exchange resins in strong acid form were used. The cation exchange resin is washed to be neutral with demineralized water before use.
In addition to the above examples, the potentiometric titrator was a Mettler DL58 potentiometric titrator, employing a photometric electrode, the wavelength was set at 555 nm.
The method for calculating the content of the sulfate comprises the following steps:
in the formula:
m is the mass of the sample, g;
0.4003 is the conversion coefficient of barium perchlorate solution to sulfur trioxide of 0.0005 mol/L;
1.2498 is the conversion coefficient of sulfur dioxide to sulfur trioxide;
The method is used for carrying out the standard addition recovery experiment of adding superior pure anhydrous sodium sulfate to the gypsum actually generated by the desulfurization system, and the experimental result is shown in Table 2
TABLE 2 result of recovery rate test of desulfurized gypsum sample
| Sample name | SO in sample3Value/mg | SO in Standard3Addition amount/mg | Measured total amount/mg | Percent recovery% |
| First-stage desulfurized gypsum | 8.96 | 8.5 | 17.2 | 98.1 |
| Second-stage desulfurized gypsum | 7.85 | 15.4 | 24.2 | 106.2 |
| Three-stage desulfurized gypsum | 8.17 | 12.6 | 21.2 | 103.4 |
Example 3 results of precision experiments
0.2500g of sample was weighed into a beaker and 10mL of H was added2O2And 10mL of demineralized water, cover the petri dish, and stir with a magnetic stirrer for 10min. Then three spoons of cation exchange resin were added and stirred for 10min the sample was filtered with filter paper into a 250mL volumetric flask, the beaker was carefully rinsed with demineralized water, filtered until the solution level was close to the neck of the 250mL volumetric flask and the volume was brought to 250mL with demineralized water. Pipette 10mL into a beaker, add 10mL of acetone and 3 drops of sulfonic acid-III indicator, mix, and slowly add demineralized water until the solution color just turns purple. Titration was carried out in a potentiometric titrator with 0.005mol/L barium perchlorate until the solution became pale blue in color. The consumption volume V is recorded.
Other test reagents: 0.005mol/L standard sulfuric acid solution for calibrating barium perchlorate.
In addition to the above examples, cation exchange resins in strong acid form were used. The cation exchange resin is washed to be neutral with demineralized water before use.
In addition to the above examples, the potentiometric titrator was a Mettler DL58 potentiometric titrator, employing a photometric electrode, the wavelength was set at 555 nm.
Still further, the method for calculating the sulfate content comprises the following steps:
in the formula:
m is the mass of the sample, g;
0.4003 is the conversion coefficient of barium perchlorate solution to sulfur trioxide of 0.0005 mol/L;
1.2498 is the conversion coefficient of sulfur dioxide to sulfur trioxide;
The method is used for carrying out precision experiments on actual desulfurized gypsum, and the experimental results are shown in Table 3
TABLE 3 results of the precision test
The principle of the invention is as follows:
oxidation of sulfite:
CaSO3→Ca2++SO3 2-
H2O2+SO3 2-→H2O+SO4 2-
and (3) sulfate determination:
CaSO4+Ba(ClO4)2→Ca(ClO4)2+BaSO4↓
although the invention has been described in detail above with reference to a general description and specific examples, it will be apparent to one skilled in the art that modifications or improvements may be made thereto based on the invention. Accordingly, such modifications and improvements are intended to be within the scope of the invention as claimed.
Claims (9)
1. A method for rapidly and accurately measuring the sulfate content in wet flue gas desulfurization gypsum is characterized by comprising the following steps:
s1, weighing 0.25g of desulfurized gypsum sample, adding 10mL of H2O2Mixing with 10mL of demineralized water, and stirring;
s2, adding cation exchange resin, stirring and filtering;
s3, placing the filtrate in a 250mL volumetric flask, repeatedly filtering and washing until the liquid level of the solution is close to the bottleneck of the 250mL volumetric flask, and fixing the volume to 250mL by using desalted water;
s4, taking 10mL of constant volume solution, adding 10mL of acetone and 3 drops of sulfonic acid-III indicator, mixing, and adding desalted water until the color of the solution is just purple;
s5, titrating the solution titrated in the step S4 on a potentiometric titrator by using 0.005mol/L barium perchlorate until the color of the solution becomes light blue, and recording the volume V of the barium perchlorate consumed by titration.
2. The method for rapidly and accurately determining the sulfate content in the wet flue gas desulfurization gypsum according to claim 1, characterized in that: in the step S1, the mixture is stirred for 10min by a magnetic stirrer.
3. The method for rapidly and accurately determining the sulfate content in the wet flue gas desulfurization gypsum according to claim 1, characterized in that: said H2O2The mass fraction is 30%.
4. The method for rapidly and accurately determining the sulfate content in the wet flue gas desulfurization gypsum according to claim 1, characterized in that: the cation exchange resin adopts strong acid type cation exchange resin.
5. The method for rapidly and accurately determining the sulfate content in the wet flue gas desulfurization gypsum according to claim 4, wherein the method comprises the following steps: the cation exchange resin was washed with demineralized water until the effluent pH was 7 prior to use.
6. The method for rapidly and accurately determining the sulfate content in the wet flue gas desulfurization gypsum according to claim 1, characterized in that: the mass fraction of sulfonic acid-III is 0.1 percent; acetone was analytically pure.
7. The method for rapidly and accurately determining the sulfate content in the wet flue gas desulfurization gypsum according to claim 1, characterized in that: the potentiometric titrator adopts a photometric electrode.
8. The method for rapidly and accurately determining the sulfate content in the wet flue gas desulfurization gypsum according to claim 1, characterized in that: the wavelength of the potentiometric titrator was set to 555 nm.
9. The method for rapidly and accurately determining the sulfate content in the wet flue gas desulfurization gypsum according to any one of claims 1 to 8, wherein the method comprises the following steps: the method for calculating the content of the sulfate comprises the following steps:
in the formula:
m is the mass of the sample, g;
0.4003 is the conversion coefficient of barium perchlorate solution to sulfur trioxide of 0.0005 mol/L;
1.2498 is the conversion coefficient of sulfur dioxide to sulfur trioxide;
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2021
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